Oil reserves based on mineable US oil sands deposits have been estimated at between 36 and 54 billion barrels of crude oil. (US Geologic Survey 2006.) Oil sand reserves in Utah alone have been estimated at between 12 and 18 billion barrels of crude oil. (USGS 2006.) For comparison, Bakken type crude oil, which is a crude oil derived from underground shale oil deposits in North Dakota, has been estimated by the USGS to have 7.4 billion barrels of technically recoverable crude oil. (2013) Although oil shale-derived crude oil has substantially different characteristics from mineable oil sands, both types of crude oils are converted to transportation fuels in US refineries. However, due to environmental concerns in the US of how crude oil is typically obtained from oil sands, essentially all of the oil sands-derived crude oil refined in the US today is imported from Canada. Nevertheless, due to the substantial quantity of crude oil that can be derived from mineable US oil sands, as well as oil sands throughout the world, there is a great interest in recovering crude oil from mineable oil sands and processing the crude oil to produce transportation fuel.
Oil sands extraction technologies in use in Canada today are based on a hot water extraction process that is designed to extract essentially all of the oily tar (˜90+%) from the oil sands. An environmentally undesirable byproduct of the hot water process is the formation of “tailings ponds,” which comprise an oil and water emulation and fine sand particles. The tailings ponds must be treated to further remove the oil and sand from the water, which can take several years. This process, therefore, raises particular environmental concerns in the US.
The oil sands extraction technologies have been historically designed to fully separate as much as possible of the oily tar (bitumen) from the sand, then send the bitumen-derived crude oil to multiple upgrade plants. In general, the upgrade plants are divided into primary upgrading and secondary upgrading plants. Primary upgrading plants include a variety of operating units such as distillation columns, cokers, hydrotreaters and hydrocrackers, which produce a synthetic type of crude oil that must be further processed in the secondary upgrading plant. The primary upgrading processes also produce a significant “petcoke” by-product, which is essentially a graphite material having little commercial utility.
The synthetic crude produced in the primary upgrading plant is then sent to a secondary upgrading plant. Secondary upgrading plants include catalytic conversion processes designed to convert the synthetic crude to useful retail products including transportation fuels.
According to Couch, Keith A., et al, “Impact of bitumen feeds on the FCCU: part I,” www.digitalrefining.com/article/1000731, PTQ Q3 2008, primary importers of Canadian bitumen-derived crude oil to the US have historically been refiners in the Rocky Mountain states (PADD IV) and Midwest (PADD II). Wider importation of bitumen-derived crude oil has been limited primarily by a lack of pipeline infrastructure to support an economically broader distribution. However, with numerous market pressures compelling refiners to consider increasing their diet of opportunity crudes, pipeline companies are actively working to upgrade their distribution capabilities by expanding mainlines to the US.
A large quantity of heavy crudes has historically been imported into the US from Western Canada. These heavy crudes have varied widely in their assay properties.
In an effort to provide a crude oil with consistent properties, a unique and standardized blend of synthetic crude, diluent and bitumen (SynDilBit) was developed by EnCana, Talisman, Canadian Natural Resources Limited (CNRL) and Petro-Canada, and has been marketed under the name of Western Canadian Select (WCS) since January 2005. WCS has essentially become the benchmark product from Western Canada, and is the crude basis on which refiners have focused on producing transportation fuels from bitumen-derived crude.
Blend specifications for WCS meet an API gravity of 19-22°, carbon residue of 7-9 wt %, sulfur of 2.8-3.2 wt %, and a total acid number (TAN) of 0.7-1.0 mg KOH/g. The resultant crude composition for WCS compared to a standard crude such as West Texas Intermediate (WTI) shows that WCS has three times more residual material than the benchmark conventional crude, West Texas Intermediate (WTI), 50% more vacuum gas oil (VGO), half the distillate and half of the naphtha.
In addition to the composition differences between WCS and more conventional crudes, the resulting VGO qualities are much lower compared to the more conventional crudes. This can be a particular problem, since the VGO must be processed through catalytic conversion processes in order produce substantial quantities of transportation fuels. Because of the low quality of the bitumen-derived crude, there is a substantial concern of the negative impact on catalytically converting the crude oil to desirable levels of transportation fuel.
Improved processes for extracting bitumen-derived crude oil from mineable oil sands are, therefore, desired to eliminate the formation of “tailings ponds.” Improved processes are also desired that produce less petroleum coke (petcoke or coke) by-product. In addition, it is desired to produce higher quality transportation fuels from bitumen-derived crude oil with less energy consumption and fewer refining steps. It is further desired to extract bitumen-derived crude oil and produce transportation fuel from the bitumen-derived crude in a manner that translates to a significantly smaller carbon “footprint.”